Biomass gasification system

ABSTRACT

A biomass gasification system for efficiently extracting heat energy from biomass material. The biomass gasification system includes a primary combustion chamber, a rotating grate within the primary combustion chamber for supporting the biomass during gasification, a feeder unit in communication with the primary combustion chamber for delivering biomass, a secondary combustion chamber fluidly connected to the primary combustion chamber, an oxygen mixer positioned between the primary combustion chamber and the secondary combustion chamber, a heat exchanger and an exhaust stack.

CROSS REFERENCE TO RELATED APPLICATIONS

[0001] Not applicable to this application.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

[0002] Not applicable to this application.

BACKGROUND OF THE INVENTION

[0003] 1. Field of the Invention

[0004] The present invention relates generally to biomass gasificationand more specifically it relates to a biomass gasification system forefficiently extracting heat energy from biomass material.

[0005] 2. Description of the Related Art

[0006] Biomass gasification processes have been in use for years forconverting biomass into an energy source. Biomass gasificationapplications include water boiling, steam generation, drying, motivepower applications (e.g. using the producer gas as a fuel in internalcombustion engines), and electricity generation.

[0007] Almost all kinds of biomass with moisture content of 5-30% can begasified. Examples of suitable biomass include forest slash, urban woodwaste, lumber waste, wood chips, sawdust, straw, firewood, agriculturalresidue, dung and the like. Under controlled conditions, characterizedby low oxygen supply and high temperatures, most biomass materials canbe converted into a gaseous fuel known as “producer gas”, which consistsof combustible mixture of nitrogen, carbon monoxide, and hydrogen. Thisthermo-chemical conversion of solid biomass into gaseous fuel is calledbiomass gasification.

[0008] Biomass gasification has many of the advantages associated withusing gaseous and liquid fuels such as clean combustion, compact burningequipment, high thermal efficiency and a good degree of control. Inlocations where biomass is already available at reasonable low prices(e.g. agricultural areas) or in industries using fuel wood, biomassgasifier systems offer definite economic advantages. Biomassgasification technology is also environment-friendly, because of thefuel savings and reduction in CO₂ emissions.

[0009] The main problems with the application of biomass gasificationsystems have been economic, not technical. For example, conventionalbiomass gasification systems are typically suitable only for large-scaleoperations and not small-scale operations. Also, the product fromgasification is mainly a heat source, and the low value of theseproducts in today's market is insufficient to justify the capital andoperating costs of conventional biomass gasification systems. Hence,there is a need for a biomass gasification system that is efficient andcost effective to operate with low cost biomass.

[0010] An example of a patented device this is related to the presentinvention is illustrated in U.S. Pat. No. 2,171,535 to Berg et al. foran incineration system for disposal of refuse having high moisturecontent. However, the Berg et al. patent reference does not have apiston feeder structure, a rotating grate within the primary combustionchamber, a silica collector system nor an oxygen mixer between theprimary combustion chamber and the secondary combustion chamber.

[0011] While these devices may be suitable for the particular purpose towhich they address, they are not as suitable for efficiently extractingheat energy from biomass material. Conventional biomass apparatus do notefficiently extract heat energy from the biomass material.

[0012] In these respects, the biomass gasification system according tothe present invention substantially departs from the conventionalconcepts and designs of the prior art, and in so doing provides anapparatus primarily developed for the purpose of efficiently extractingheat energy from biomass material.

BRIEF SUMMARY OF THE INVENTION

[0013] In view of the foregoing disadvantages inherent in the knowntypes of gasification apparatus now present in the prior art, thepresent invention provides a new biomass gasification systemconstruction wherein the same can be utilized for efficiently extractingheat energy from biomass material.

[0014] The general purpose of the present invention, which will bedescribed subsequently in greater detail, is to provide a new biomassgasification system that has many of the advantages of the gasificationapparatus mentioned heretofore and many novel features that result in anew biomass gasification system which is not anticipated, renderedobvious, suggested, or even implied by any of the prior art gasificationapparatus, either alone or in any combination thereof.

[0015] To attain this, the present invention generally comprises aprimary combustion chamber, a rotating grate within the primarycombustion chamber for supporting the biomass during gasification, afeeder unit in communication with the primary combustion chamber fordelivering biomass, a secondary combustion chamber fluidly connected tothe primary combustion chamber, an oxygen mixer positioned between theprimary combustion chamber and the secondary combustion chamber, a heatexchanger and an exhaust stack.

[0016] There has thus been outlined, rather broadly, the more importantfeatures of the invention in order that the detailed description thereofmay be better understood, and in order that the present contribution tothe art may be better appreciated. There are additional features of theinvention that will be described hereinafter and that will form thesubject matter of the claims appended hereto.

[0017] In this respect, before explaining at least one embodiment of theinvention in detail, it is to be understood that the invention is notlimited in its application to the details of construction and to thearrangements of the components set forth in the following description orillustrated in the drawings. The invention is capable of otherembodiments and of being practiced and carried out in various ways.Also, it is to be understood that the phraseology and terminologyemployed herein are for the purpose of the description and should not beregarded as limiting.

[0018] A primary object of the present invention is to provide a biomassgasification system that will overcome the shortcomings of the prior artdevices.

[0019] A second object is to provide a biomass gasification system forefficiently extracting heat energy from biomass material.

[0020] Another object is to provide a biomass gasification system thatprovides for usage of biomass gasification technologies withinsmall-scale operations.

[0021] An additional object is to provide a biomass gasification systemthat is capable of utilizing various types of biomass materials readilyavailable.

[0022] A further object is to provide a biomass gasification system thatprovides a cost effective alternative fuel source compared toconventional fossil fuels.

[0023] Another object is to provide a biomass gasification system thatis environmentally friendly and utilizes renewable resources.

[0024] A further object is to provide a biomass gasification system thathas efficiency ratings approaching 85%.

[0025] Another object is to provide a biomass gasification system thatis automated and requires reduced maintenance.

[0026] A further object is to provide a biomass gasification system thatmay be utilized to produce beat, mechanical power or electricity.

[0027] Other objects and advantages of the present invention will becomeobvious to the reader and it is intended that these objects andadvantages are within the scope of the present invention.

[0028] To the accomplishment of the above and related objects, thisinvention may be embodied in the form illustrated in the accompanyingdrawings, attention being called to the fact, however, that the drawingsare illustrative only, and that changes may be made in the specificconstruction illustrated and described within the scope of the appendedclaims.

BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Various other objects, features and attendant advantages of thepresent invention will become fully appreciated as the same becomesbetter understood when considered in conjunction with the accompanyingdrawings, in which like reference characters designate the same orsimilar parts throughout the several views, and wherein:

[0030]FIG. 1 is a side cutaway view of the present invention.

[0031]FIG. 2 is a side view of the fuel magazine and disintegrationunit.

[0032]FIG. 3 is a side cutaway view of the primary combustion chamber.

[0033]FIG. 4 is a side cutaway view of the secondary combustion chamber.

[0034]FIG. 5 is a side cutaway view of the heat exchanger.

[0035]FIG. 6 is a side cutaway view of the exhaust stack.

[0036]FIGS. 7a-7 c illustrate the operation of the feeder unit.

[0037]FIG. 8 is a side cutaway view of the primary combustion chamberwith the fuel conveyor and disintegration unit.

[0038]FIG. 9 is a magnified side view of the fuel conveyor feedingbiomass into the feeder unit.

[0039]FIG. 10 is a block diagram illustrating the overall control systemfor the present invention.

DETAILED DESCRIPTION OF THE INVENTION

[0040] A. Overview

[0041] Turning now descriptively to the drawings, in which similarreference characters denote similar elements throughout the severalviews, FIGS. 1 through 10 illustrate a biomass gasification sysem 10,which comprises a primary combustion chamber 20, a rotating grate 21within the primary combustion chamber 20 for supporting the biomassduring gasification, a feeder unit 70 in communication with the primarycombustion chamber 20 for delivering biomass, a secondary combustionchamber 40 fluidly connected to the primary combustion chamber 20, anoxygen mixer 30 positioned between the primary combustion chamber 20 andthe secondary combustion chamber 40, a heat exchanger 50 and an exhauststack 60.

[0042] B. Primary Combustion Chamber

[0043] The primary combustion chamber 20 is where the primary combustionoccurs thereby converting the biomass to a producer gas as shown inFIGS. 1, 3 and 8 of the drawings. The primary combustion chamber 20 maybe comprised of various structures commonly utilized within thegasification industry.

[0044] The interior portion of the primary combustion chamber 20 ispreferably circular for receiving the rotating grate 21, however variousother interior cross sectional shapes may be utilized to construct theprimary combustion chamber 20. The primary combustion chamber 20 ispreferably formed for gasifying various types of biomass such as but notlimited to forest slash, urban wood waste, lumber waste, wood chips,sawdust, straw, firewood, agricultural residue, dung and the like.

[0045] As shown in FIGS. 1 and 3 of the drawings, an ash disposal unit23 is preferably positioned beneath the rotating grate 21 for removingcollected ash from the primary combustion chamber 20. The ash disposalunit 23 may be comprised of any well-known technology capable ofremoving ash from the primary combustion chamber 20.

[0046] C. Rotating Grate

[0047] As shown in FIGS. 1, 3 and 8 of the drawings, the rotating grate21 is rotatably positioned within a lower portion of the primarycombustion chamber 20 for supporting the biomass during gasification.The rotating grate 21 preferably has a flat structure, however variousother structures may be utilized to construct the rotating grate 21. Therotating grate 21 may be comprised of various rigid materials capable ofwithstanding high temperatures such as but not limited to metal.

[0048] The rotating grate 21 preferably includes a plurality of openingswithin it for allowing air to pass upwardly through the biomasspositioned upon the rotating grate 21 thereby feeding the primarycombustion. The openings within the rotating grate 21 may have varioussizes, shapes and patterns that allow air to pass through into thebiomass as can be appreciated.

[0049] The rotating grate 21 preferably has a shape and size similar toan interior of the primary combustion chamber 20 thereby preventingbiomass from falling between the outer perimeter of the rotating grate21 and the inner wall of the primary combustion chamber 20. The rotatinggrate 21 is rotatably supported within the lower portion of the primarycombustion chamber 20 utilizing a support structure within the primarycombustion chamber 20. The rotating grate 21 preferably is substantiallytransverse with respect to a longitudinal axis of the primary combustionchamber 20 as shown in FIGS. 1, 3 and 8 of the drawings.

[0050] In addition, a drive motor 27 is mechanically connected to therotating grate 21 for rotating the rotating grate 21. The drive motor 27may be comprised of any well-known motor structure such as electric,hydraulic and the like. The drive motor 27 may be mechanically connectedto the rotating grate 21 via various conventional connection means suchas gears, chains, drive shaft 76 and the like.

[0051] As shown in FIGS. 1 and 3 of the drawings, an air distributionsystem 22 is positioned within the primary combustion chamber 20 beneaththe rotating grate 21 for forcing air beneath the rotating grate 21through the openings. The air distribution system 22 draws fresh airfrom outside of the primary combustion chamber 20 into the primarycombustion area to assist in increasing the temperature of the primarycombustion. The air distribution system 22 may be comprised of variousdevices capable of forcing air into the primary combustion chamber 20.

[0052] D. Feeder Unit

[0053] The feeder unit 70 is in communication with the primarycombustion chamber 20 for delivering biomass onto the rotating grate 21as shown in FIGS. 1 and 8 of the drawings. The feeder unit 70 preferablyincludes a disintegration unit 26 for disintegrating the biomass beforeentering the primary combustion chamber 20, thereby increasing the rateof breakdown for the biomass within the primary combustion chamber 20.

[0054] The feeder unit 70 also preferably includes a biomass magazine 25capable of storing a volume of the biomass for inputting biomass intothe disintegration unit 26. For example, if straw bales are used in thepresent invention as the biomass, then the biomass magazine 25 would becapable of delivering bales of the straw into the disintegration upondemand. A biomass storage bin 24 stores a volume of the biomass prior toentering the biomass magazine 25. The biomass storage bin 24 may becapable of storing various volumes of biomass.

[0055] As shown in FIGS. 7a-7 c of the drawings, the feeder unit 70preferably includes a plunger member 78 that pushes the biomass into anopening surrounded by an input member 29 within the primary combustionchamber 20 onto the rotating grate 21. The plunger member 78 is slidablypositioned within the input member 29 as illustrated in FIGS. 7a-7 c ofthe drawings.

[0056] The opening within the primary combustion unit is preferablyaligned with or slightly above the upper surface of the rotating grate21 as shown in FIGS. 7a-7 c and 9 of the drawings. The input member 29is preferably comprised of a tubular structure that allows forcing ofthe biomass into the primary combustion chamber 20 as shown in FIGS.7a-7 c of the drawings.

[0057] The plunger member 78 moves along a path radial to the rotatinggrate 21 and has a cyclical action. The cyclical action of the plungermember 78 allows for new biomass to be inserted into the primarycombustion chamber 20 as the rotating grate 21 rotates. As the newbiomass is forced onto the rotating grate 21, the remaining biomass isforced inwardly and the ashes pass through the rotating grate 21 toallow for the new biomass.

[0058] The feeder unit 70 preferably includes a conveyor 28 positionedbetween the disintegration unit 26 and the primary combustion chamber 20for transferring the particulate biomass into the primary combustionchamber 20. The conveyor 28 positions the new biomass into an upperopening within the input member 29 where after the plunger member 78drives the biomass into the primary combustion chamber 20.

[0059] Various well-known mechanical devices may reciprocally drive theplunger member 78. A suitable mechanical device for driving the plungermember 78 is comprised of a flywheel 74 connected to a motor unit 72 anda drive shaft 76 attached to an outer portion of the flywheel 74 and tothe plunger member 78. Various other devices may be utilized to drivethe plunger member 78. In addition, various other structures may beutilized to input the biomass into the primary combustion chamber 20instead of the plunger member 78.

[0060] E. Oxygen Mixer

[0061] The oxygen mixer 30 is positioned between the primary combustionchamber 20 and the secondary combustion chamber 40 as best shown in FIG.1 of the drawings. The oxygen mixer 30 is in communication with thecontrol unit 12 and allows a desired volume of oxygen or air into thetransfer tube 32 positioned between the primary combustion chamber 20and the secondary combustion chamber 40. The transfer tube 32 preferablyhas a cross section substantially smaller than the primary combustionchamber 20 to create a high velocity jet stream of producer gas enteringthe secondary combustion chamber 40.

[0062] The oxygen mixer 30 preferably inputs the oxygen into theproducer gas emitted from the biomass in the primary combustion chamber20 to increase the temperature of the secondary combustion to 2,000+degrees Fahrenheit. As the producer gas increases in volume andvelocity, the oxygen mixer 30 ensures that sufficient oxygen existsprior to entering the secondary combustion within the upper portion ofthe secondary combustion chamber 40.

[0063] F Secondary Combustion Chamber

[0064] The secondary combustion chamber 40 is fluidly connected to theprimary combustion chamber 20 via the transfer tube 32 at the upperportions thereof as best shown in FIG. 1 of the drawings. The secondcombustion chamber preferably has a substantially smaller cross sectionthan the primary combustion chamber 20 for increasing the velocity ofthe gases.

[0065] As the producer gas and oxygen enter the upper portion of thesecond combustion chamber, a secondary combustion is formed that canexceed 2,000+ degrees Fahrenheit. At this temperature, contaminants andother material are burned completely thereby providing a clean andreduced pollution exhaust.

[0066] In addition, silica in the form of liquid typically is formed onthe inner walls of the secondary combustion chamber 40 that is collectedwithin the silica collector 42 at the bottom of the secondary combustionchamber 40 as shown in FIGS. 1 and 4 of the drawings. The silica may becollected into various types of containers such as but not limited tocarts.

[0067] Alternatively, a liquid may be positioned within the silicacontainer that pulverizes the silica chunks that fall into at an extremetemperature, where after the silica debris may be cleaned from theliquid. The silica collector 42 prevents the buildup of silica withinthe secondary combustion chamber 40 when straw and similar biomass areutilized with relatively high silica content.

[0068] G. Heat Exchanger

[0069] The heat exchanger 50 is fluidly connected to a lower portion ofthe secondary combustion chamber 40 as best shown in FIGS. 1 and 5 ofthe drawings. The heat exchanger 50 preferably includes a particlecollector 52 for collecting particle waste remaining within the exhaustof the secondary combustion that falls downwardly from within the heatexchanger 50.

[0070] It can be appreciated that a conventional heat exchanger 50 maybe utilized that allows cool water to enter into pipes within the heatexchanger 50 that conduct the heat from the highly heated exhaust gas.The hot water then exits the heat exchanger 50 for use in producingelectricity, heat for thermal applications and the like.

[0071] The preferred structure for a heat exchanger 50 is shown in FIG.5 wherein a fluid tank retaining a volume of water or other liquid has aplurality of exhaust pipes passing through thereof. The heated exhaustgas passes through the exhaust pipes within the fluid tank therebyheating the liquid within the fluid tank. An auger structure is utilizedto remove collected particle waste from within the interior of theexhaust pipes.

[0072] H. Control Unit

[0073] As shown in FIG. 10 of the drawings, the control unit 12 is incommunication with the oxygen mixer 30, the disintegration unit 26, thefeeder unit 70, the air distribution system 22, the exhaust blower 62,the drive motor 27 and the fuel conveyor 28. The control unit 12 may bein communication with these devices via direct electrical connection,radio signal or other communication means.

[0074] The control unit 12 also is in communication with various sensors14 within the primary combustion chamber 20, the secondary combustionchamber 40, the heat exchanger 50 and the exhaust stack 60 to monitorthe performance of the system and adjust the components accordingly. Thecontrol unit 12 may be comprised of a computer or other electronicdevice capable of storing various types of data including input data,program data and the like.

[0075] I. Operation

[0076] In use, the biomass is loaded within the biomass storage bin 24.The biomass is then automatically loaded into the biomass magazine 25which then feeds the biomass into the disintegration unit 26. The brokendown biomass is then transferred along the conveyor 28 into the primarycombustion chamber 20. The biomass is fed into the input member 29 whereafter the plunger member 78 forces the biomass into the primarycombustion chamber 20 onto the rotating grate 21 as shown in FIGS. 7a-7c of the drawings. The new biomass within the primary combustion chamber20 is thereafter broken down by the primary combustion within theprimary combustion chamber 20 into producer gas. The producer gas risesto the upper portion of the interior of the primary combustion chamber20 and then enters the transfer tube 32. As the producer gas passesthrough the transfer tube 32 a high velocity, the oxygen mixer 30 inputsoxygen within the producer gas which is then dispersed into the upperportion of the secondary combustion chamber 40 where the secondarycombustion occurs at a high temperature (exceeding 2,000 degreeFahrenheit). Silica and other debris is collected within the silicacollector 42 at the bottom of the secondary combustion chamber 40. Thesuper heated exhaust gas then enters the heat exchanger 50 to heat aliquid or perform another function for transferring the heat energy. Thecooled exhaust gas thereafter passes downwardly to a lower portion of anexhaust stack 60 where an exhaust blower 62 assists in transferring thecooled exhaust gas outwardly through the exhaust stack 60.

[0077] As to a further discussion of the manner of usage and operationof the present invention, the same should be apparent from the abovedescription. Accordingly, no further discussion relating to the mannerof usage and operation will be provided.

[0078] With respect to the above description then, it is to be realizedthat the optimum dimensional relationships for the parts of theinvention, to include variations in size, materials, shape, form,function and manner of operation, assembly and use, are deemed to bewithin the expertise of those skilled in the art, and all equivalentstructural variations and relationships to those illustrated in thedrawings and described in the specification are intended to beencompassed by the present invention.

[0079] Therefore, the foregoing is considered as illustrative only ofthe principles of the invention. Further, since numerous modificationsand changes will readily occur to those skilled in the art, it is notdesired to limit the invention to the exact construction and operationshown and described, and accordingly, all suitable modifications andequivalents may be resorted to, falling within the scope of theinvention.

1. A biomass gasification system, comprising: a primary combustion chamber; a secondary combustion chamber fluidly connected to said primary combustion chamber; a heat exchanger fluidly connected to said secondary combustion chamber; and a rotating grate rotatably positioned within said primary combustion chamber for supporting the biomass during gasification, wherein said rotating grate is capable of rotating in a continuous rotational manner.
 2. The biomass gasification system of claim 1, including an oxygen mixer positioned between said primary combustion chamber and said secondary combustion chamber.
 3. The biomass gasification system of claim 1, including a feeder unit in communication with said primary combustion chamber for delivering biomass onto said rotating grate.
 4. The biomass gasification system of claim 3, wherein said feeder unit includes a disintegration unit for disintegrating the biomass before entering said primary combustion chamber.
 5. The biomass gasification system of claim 4, wherein said feeder unit includes a fuel magazine capable of storing a volume of the biomass for inputting biomass into said disintegration unit.
 6. The biomass gasification system of claim 2, wherein said feeder unit includes a plunger member that pushes the biomass into an opening within said primary combustion chamber onto said rotating grate.
 7. The biomass gasification system of claim 6, wherein said plunger member moves along a path radial to said rotating grate.
 8. The biomass gasification system of claim 6, wherein said plunger member has a cyclical action.
 9. The biomass gasification system of claim 6, wherein said opening within said primary combustion chamber is surrounded by an input member having a tubular structure, wherein said plunger member is slidably positioned within said input member and wherein a front end of said plunger member extends near an interior of said primary combustion chamber.
 10. The biomass gasification system of claim 4, wherein said feeder unit includes a conveyor positioned between said disintegration unit and said primary combustion chamber.
 11. The biomass gasification system of claim 1, wherein said rotating grate includes a plurality of openings within for allowing air to pass upwardly through the biomass positioned upon said rotating grate.
 12. The biomass gasification system of claim 11, including an air distribution system for forcing air beneath said rotating grate through said openings.
 13. The biomass gasification system of claim 1, including an ash disposal unit positioned beneath said rotating grate for removing collected ash from said primary combustion chamber.
 14. The biomass gasification system of claim 1, wherein said rotating grate includes a plurality of openings within for allowing air to pass upwardly through the biomass positioned upon said rotating grate.
 15. The biomass gasification system of claim 1, including a drive motor mechanically connected to said rotating grate for rotating said rotating grate.
 16. A biomass gasification system, comprising: a primary combustion chamber; a rotating grate rotatably positioned within said primary combustion chambers wherein said rotating grate has a substantially planar upper surface for supporting the biomass during gasification, wherein said rotating grate is capable of rotating in a continuous rotational manner; and a drive motor mechanically connected to said rotating grate for rotating said rotating grate.
 17. The biomass gasification system of claim 16, including a feeder unit in communication with said primary combustion chamber for delivering biomass onto said rotating grate.
 18. The biomass gasification system of claim 17, wherein said feeder unit includes a plunger member that pushes the biomass into an opening within said primary combustion chamber onto said rotating grate.
 19. The biomass gasification system of claim 16, wherein said rotating grate includes a plurality of openings within for allowing air to pass upwardly through the biomass positioned upon said rotating grate.
 20. The biomass gasification system of claim 16, including an air distribution system for forcing air beneath said rotating grate through said openings. 